The aim of this proposal is to investigate the possible correlation between the pharmacokinetics of preddnisone and prednisolone with measures of clinical efficacy and toxicity in patients with oral inflammatory disease. STudies will be carried out in patients with lichen planus, erythema multiforme, mucous membrane pemphigoid and pemphigus vulgaris. Using a sensitive and specific high performance liquid chromatographic assay and equilibrium dialysis, the parhmacokinetics of prednisone and prednisolone will be investigated in this patient population following oral and intravenous corticosteroid dosing. From the kinetic values, measures of bioavailability, clearance of total and unbound drug, volume of distribution and terminal half-life will be followed.